do not force write of packed refs

We force writing a ref if it does not exist. Originally, we only had to look
for the ref file to check if it existed. Now we have to look for a packed ref
as well. Luckily, resolve_ref already does all the work for us.

Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -788,10 +788,10 @@ static struct ref_lock *lock_ref_sha1_basic(const char *ref, const unsigned char
 	char *ref_file;
 	const char *orig_ref = ref;
 	struct ref_lock *lock;
-	struct stat st;
 	int last_errno = 0;
 	int type, lflags;
 	int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
+	int missing = 0;
 
 	lock = xcalloc(1, sizeof(struct ref_lock));
 	lock->lock_fd = -1;
@@ -819,12 +819,13 @@ static struct ref_lock *lock_ref_sha1_basic(const char *ref, const unsigned char
 			orig_ref, strerror(errno));
 		goto error_return;
 	}
+	missing = is_null_sha1(lock->old_sha1);
 	/* When the ref did not exist and we are creating it,
 	 * make sure there is no existing ref that is packed
 	 * whose name begins with our refname, nor a ref whose
 	 * name is a proper prefix of our refname.
 	 */
-	if (is_null_sha1(lock->old_sha1) &&
+	if (missing &&
             !is_refname_available(ref, NULL, get_packed_refs(), 0))
 		goto error_return;
 
@@ -838,7 +839,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *ref, const unsigned char
 	lock->ref_name = xstrdup(ref);
 	lock->orig_ref_name = xstrdup(orig_ref);
 	ref_file = git_path("%s", ref);
-	if (lstat(ref_file, &st) && errno == ENOENT)
+	if (missing)
 		lock->force_write = 1;
 	if ((flags & REF_NODEREF) && (type & REF_ISSYMREF))
 		lock->force_write = 1;

t/t3210-pack-refs.sh

@@ -96,6 +96,13 @@ test_expect_success \
      git branch -d n/o/p &&
      git branch n'
 
+test_expect_success \
+	'see if up-to-date packed refs are preserved' \
+	'git branch q &&
+	 git pack-refs --all --prune &&
+	 git update-ref refs/heads/q refs/heads/q &&
+	 ! test -f .git/refs/heads/q'
+
 test_expect_success 'pack, prune and repack' '
 	git tag foo &&
 	git pack-refs --all --prune &&